Well, I can't sit quietly through any more of this. As I said earlier, pink ring is by no means a new phenonmenon, and several articles were written about 8-10 years ago. They were the ones I listed, plus of course there were/are others. Let me just say, some people dealt with pink ring in these ways: 1) Redesign or reconstruct the board so the oxide layer points inward and you can't see the PR. 2) Use a dark laminate or polyimide, so you can't see the contrast. 3) Use a red oxide, which is much lighter, so you can't see the contrast. 4) Hide it with solder mask. Some others blamed their electroless and electroplating and sometimes the oxide suppliers. When I worked for Enthone we learned a lot about lamination and drilling, etc., in order to determine if it really was a chemical problem. We spent a lot of time teaching customers how to make their boards better. But, also, I don't believe that PR was as much problem prior to that time, because boards were simpler: there weren't as many layers; the drilled holes were larger and further apart, plus people didn't drill more than 1 or 2 high because production needs were low; only the "high tech" companies were making the MLs; and/or (maybe) the FR-4 lamination process in use was a little more forgiving (i.e., heat-up and cool-down were not rushed to get out more production). It gets back to what the articles say, that pink ring is an Indicator of other process problems, and those problems can begin back as far as the quality of the pre-preg to be used in lamination. Optimization of the copper-oxide-resin (C-O-R) bond that is created during lamination (by optimizing the oxiding, lamination and drill processes) is the key to reducing or eliminating PR. The danger of the oxide reduction processes, and other means that hide pink ring, is that THEY DON'T ADDRESS THE REAL CONCERNS OF A WEAK OR POOR THE C-O-R BOND. Therefore, if you just try to hide the PR, do you have a good bond or don't you? So, optimize the processes first, starting with the first process, and use the amount of PR found as an indicator of how well you are optimizing. Then, when you have optimized as best possible, and know you have a strong C-O-R bond, THEN decide if you want to use an oxide reduction process. Note: some of the oxide reduction processes may be able to improve the C-O-R bond beyond what regular oxide can give you. But, as you optimize the whole manufacturing process, you should be able to determine that. Patty ---------- From: tgyee To: TechNet Subject: Re[5]: Mechanism of Wedge Void Formation Date: Monday, July 21, 1997 10:19AM How come chemical vendors almost always emphasize that their oxides are converted/reduced? Is the reduction process a relatively new technology? If so, before the reduction process is available, how did PCB shops prevent pink ring formation? The reason I ask is that, since there is a "pink ring" solution - reduction of oxide, whenever there is pink ring occurence, one would point at the reduction process by first instinct, forgiving other possible pink ring causes. We once faced an extremely painful pink ring crisis, and were able to end it by improving the oxide reduction process. However, during the crisis, I found out that I can separate the oxide-coated copper from the prepreg by using a knife. It was that easy even without thermal-shocking the board. And after the separation there was not even a bit of oxide seen on the prepreg side. I considered this as an evidence of poor lamination. Although we solve the pink ring by oxide reduction, I think may be we might not have the problem in the first place if the lamination is in perfect contition. *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************